Hierarchical porous ZnWO4 microspheres synthesized by ultrasonic spray pyrolysis: Characterization, mechanistic and photocatalytic NO removal studies

Abstract

Solar-light-driven photocatalysts with porous structure are preferred for gaseous pollutants removal at low concentration levels. In this study, hierarchical porous ZnWO4 microspheres were synthesized by a facile ultrasonic spray pyrolysis method for the first time. The as-prepared ZnWO4 samples were composed of microspheres with diameter ranging from 0.1 to 2 μm and it was revealed that these microspheres are formed by the self-assembly of nanoparticles. The photocatalytic performances of these microspheres were evaluated by the degradation of gaseous NOx under simulated solar light irradiation. It was found that the ZnWO4 batch synthesized at 700 °C exhibited superior photocatalytic activity to those synthesized at 650 °C and 750 °C as well as Degussa TiO2 P25. Both •OH and O2•radicals were found to be the major reactive species involved for NOx degradation as identified by electron spin resonance spectroscopy (ESR) method, which was consistent with the theoretical analysis. The excellent catalytic activity of ZWO-700 was attributed to its special hierarchical porous structure, which facilitated the separation/diffusion of the photogenerated charge carriers and the diffusion of intermediates and final products of NOx oxidation. The photocatalytic NOx removal mechanism over ZnWO4 samples was also proposed. This study suggests that ultrasonic spray pyrolysis is a facile and scalable process to fabricate ZnWO4 porous microspheres which are promising photocatalytic materials for gaseous pollutants purification.

Fabrication of Bi2O2CO3/g-C3N4 heterojunctions for efficiently photocatalytic NO in air removal: In-situ self-sacrificial synthesis, characterizations and mechanistic study

“…As an alternative to conventional approaches (selective catalytic reduction and wet scrubbing, etc.) with high cost adopted for high-concentration NO x treatment [7], semiconductor photocatalysis has gained considerable attention not only because of its potential value in addressing the worldwide energy shortage, but also because of its eco-friendly merit and high efficiency for the remediation of NO x at part-per-billion (ppb) levels [8][9][10][11][12][13].…”

Perovskite LaFeO3-SrTiO3 composite for synergistically enhanced NO removal under visible light excitation

“…The as-prepared materials are thoroughly characterized and analyzed for the promotional effect on photocatalytic reactions. 6 conical filter flask and a vacuum pump which was described in our previous study [24]. In a typical synthesis, the temperature of the tube furnace was pre-set at 800 o C, then the precursor was nebulized at a ultrasound frequency of 1.7 MHz±10%, with the atomized droplets flowing through the tube furnace in air under the pump extraction force, and finally LaFeO 3 samples (denoted as LFO) were collected in the filter flask.…”

Enhanced photocatalytic removal of NO over titania/hydroxyapatite (TiO2/HAp) composites with improved adsorption and charge mobility ability

“…Several techniques have been developed for removing NO x , such as electrochemical methods, 2 a chemical absorption-biological reduction integrated system, 3 selective catalytic reduction 4 and semiconductor photocatalysis. 5 Among these methods, semiconductor photocatalysis is a promising technology for low concentration air purication, because it allows for the utilization of renewable, safe and clean solar light to solve environmental problems.…”